Since the seventh year of Cambyses II began in spring of 523 B.C.E., his first year of rule was 529 B.C.E. and his accession year, and the last year of Cyrus II as king of Babylon, was 530 B.C.E. The latest tablet dated in the reign of Cyrus II is from the 5th month, 23rd day of his 9th year. (Babylonian Chronology, 626 B.C.–A.D. 75, by R. Parker and W. Dubberstein, 1971, p. 14) As the ninth year of Cyrus II as king of Babylon was 530 B.C.E., his first year according to that reckoning was 538 B.C.E. and his accession year was 539 B.C.E.

The date of 539 B.C.E. for the fall of Babylon can be arrived at not only by Ptolemy’s canon but by other sources as well. The historian Diodorus, as well as Africanus and Eusebius, shows that Cyrus’ first year as king of Persia corresponded to Olympiad 55, year 1 (560/559 B.C.E.), while Cyrus’ last year is placed at Olympiad 62, year 2 (531/530 B.C.E.). Cuneiform tablets give Cyrus a rule of nine years over Babylon, which would therefore substantiate the year 539 as the date of his conquest of Babylon.​—Handbook of Biblical Chronology, by Jack Finegan, 1964, pp. 112, 168-170; Babylonian Chronology, 626 B.C.–A.D. 75, p. 14; see comments above under “Babylonian Chronology,” also PERSIA, PERSIANS.